Emerson 21V51U-843 Universal Integrated Furnace Control Kit with Variable Speed Circulator Variable speed circulator output for ECM (Electronically Commutated Motor) Dipswitch selectable for OEM applications two-speed inducer output, two-stage gas valve output Pushbutton fault history retrieval Heat fan off delay (dipswitch selectable), fan on delay for cooling, and auto second-stage delay Includes 21D64-2 Silicon Nitride ignitor kit, module and wiring harness